[clang][bytecode] Fix diagnostic in final ltor cast (llvm#105292)

Don't diagnose volatile reads but diagnose a few other accesses earlier.

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -2556,7 +2556,7 @@ bool Compiler<Emitter>::VisitCXXConstructExpr(const CXXConstructExpr *E) {
 
     if (DiscardResult)
       return this->emitPopPtr(E);
-    return true;
+    return this->emitFinishInit(E);
   }
 
   if (T->isArrayType()) {

clang/lib/AST/ByteCode/EvalEmitter.cpp

@@ -165,11 +165,16 @@ template <> bool EvalEmitter::emitRet<PT_Ptr>(const SourceInfo &Info) {
   if (ConvertResultToRValue) {
     if (!Ptr.isZero() && !Ptr.isDereferencable())
       return false;
+
+    if (S.getLangOpts().CPlusPlus11 && Ptr.isBlockPointer() &&
+        !CheckFinalLoad(S, OpPC, Ptr)) {
+      return false;
+    }
+
     // Never allow reading from a non-const pointer, unless the memory
     // has been created in this evaluation.
-    if (!Ptr.isZero() && Ptr.isBlockPointer() &&
-        Ptr.block()->getEvalID() != Ctx.getEvalID() &&
-        (!CheckLoad(S, OpPC, Ptr, AK_Read) || !Ptr.isConst()))
+    if (!Ptr.isZero() && !Ptr.isConst() && Ptr.isBlockPointer() &&
+        Ptr.block()->getEvalID() != Ctx.getEvalID())
       return false;
 
     if (std::optional<APValue> V =

clang/lib/AST/ByteCode/Interp.cpp

@@ -559,6 +559,31 @@ bool CheckLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
   return true;
 }
 
+/// This is not used by any of the opcodes directly. It's used by
+/// EvalEmitter to do the final lvalue-to-rvalue conversion.
+bool CheckFinalLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
+  if (!CheckLive(S, OpPC, Ptr, AK_Read))
+    return false;
+  if (!CheckConstant(S, OpPC, Ptr))
+    return false;
+
+  if (!CheckDummy(S, OpPC, Ptr, AK_Read))
+    return false;
+  if (!CheckExtern(S, OpPC, Ptr))
+    return false;
+  if (!CheckRange(S, OpPC, Ptr, AK_Read))
+    return false;
+  if (!CheckActive(S, OpPC, Ptr, AK_Read))
+    return false;
+  if (!CheckInitialized(S, OpPC, Ptr, AK_Read))
+    return false;
+  if (!CheckTemporary(S, OpPC, Ptr, AK_Read))
+    return false;
+  if (!CheckMutable(S, OpPC, Ptr))
+    return false;
+  return true;
+}
+
 bool CheckStore(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   if (!CheckLive(S, OpPC, Ptr, AK_Assign))
     return false;

clang/lib/AST/ByteCode/Interp.h

@@ -92,6 +92,7 @@ bool CheckMutable(InterpState &S, CodePtr OpPC, const Pointer &Ptr);
 /// Checks if a value can be loaded from a block.
 bool CheckLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
                AccessKinds AK = AK_Read);
+bool CheckFinalLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr);
 
 bool CheckInitialized(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
                       AccessKinds AK);

clang/test/CXX/temp/temp.arg/temp.arg.nontype/p1-11.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -std=c++11 %s -verify -triple x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++11 %s -verify -triple x86_64-linux-gnu -fexperimental-new-constant-interpreter
 
 namespace std {
   typedef decltype(nullptr) nullptr_t;